Fix build for systems without POSIX truncate

Older versions of newlib do not provide truncate so add a configure
check for it, and provide a fallback definition.

There were also some missing exports in the linker script, which went
unnoticed because there are no tests for some functions. A new link-only
test checks that every filesystem operation function is defined by the
library.

	* acinclude.m4 (GLIBCXX_CHECK_FILESYSTEM_DEPS): Check for truncate.
	* config.h.in: Regenerate.
	* config/abi/pre/gnu.ver: Order patterns for filesystem operations
	alphabetically and add missing entries for copy_symlink,
	hard_link_count, rename, and resize_file.
	* configure: Regenerate.
	* src/c++17/fs_ops.cc (resize_file): Remove #if so posix::truncate is
	used unconditionally.
	* src/filesystem/ops-common.h (__gnu_posix::truncate)
	[!_GLIBCXX_HAVE_TRUNCATE]: Provide fallback definition that only
	supports truncating to zero length.
	* testsuite/27_io/filesystem/operations/all.cc: New test.
	* testsuite/27_io/filesystem/operations/resize_file.cc: New test.

From-SVN: r267647

2 files changed, 19 insertions, 4 deletions

diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index fd8cf353ba2..edd9315980b 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -1268,16 +1268,12 @@ fs::resize_file(const path& p, uintmax_t size)
 void
 fs::resize_file(const path& p, uintmax_t size, error_code& ec) noexcept
 {
-#ifdef _GLIBCXX_HAVE_UNISTD_H
   if (size > static_cast<uintmax_t>(std::numeric_limits<off_t>::max()))
     ec.assign(EINVAL, std::generic_category());
   else if (posix::truncate(p.c_str(), size))
     ec.assign(errno, std::generic_category());
   else
     ec.clear();
-#else
-  ec = std::make_error_code(std::errc::not_supported);
-#endif
 }
 
 
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index f20867c217e..55e482ff8f2 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -29,6 +29,9 @@
 
 #ifdef _GLIBCXX_HAVE_UNISTD_H
 # include <unistd.h>
+# ifdef _GLIBCXX_HAVE_FCNTL_H
+#  include <fcntl.h>  // AT_FDCWD, O_TRUNC etc.
+# endif
 # if defined(_GLIBCXX_HAVE_SYS_STAT_H) && defined(_GLIBCXX_HAVE_SYS_TYPES_H)
 #  include <sys/types.h>
 #  include <sys/stat.h>
@@ -139,7 +142,23 @@ namespace __gnu_posix
   using ::utime;
 # endif
   using ::rename;
+# ifdef _GLIBCXX_HAVE_TRUNCATE
   using ::truncate;
+# else
+  inline int truncate(const char* path, off_t length)
+  {
+    if (length == 0)
+      {
+	const int fd = ::open(path, O_WRONLY|O_TRUNC);
+	if (fd == -1)
+	  return fd;
+	::close(fd);
+	return 0;
+      }
+    errno = ENOTSUP;
+    return -1;
+  }
+# endif
   using char_type = char;
 #else // ! _GLIBCXX_FILESYSTEM_IS_WINDOWS && ! _GLIBCXX_HAVE_UNISTD_H
   inline int open(const char*, int, ...) { errno = ENOTSUP; return -1; }